Field of the Invention
The present invention relates to an image processing apparatus used in ophthalmological diagnosis and treatment, and to a control method of the image processing apparatus.
Description of the Related Art
Examination of the eye is widely performed for early diagnosis and treatment of lifestyle diseases and diseases which are primary causes of loss of eyesight. The scanning laser ophthalmoscope (SLO), which is an ophthalmological apparatus that employs the principle of confocal laser scanning microscopy, performs raster scanning of a laser, which is measurement light, over the fundus, and acquires a high-resolution planar image from the intensity of returning light at high speed. An apparatus which images such a planar image will hereinafter be referred to as an SLO apparatus, and the planar image to as an SLO image.
In recent years, increased beam diameter of measurement light in SLO apparatuses has enabled acquisition of SLO images of the retina, with improved horizontal resolution. However, the increased beam diameter of the measurement light has led to a problem of deterioration the S/N ratio and the resolution of the SLO image during acquisition of SLO images of the retina, due to aberration of the eye being examined. An adaptive optic SLO apparatus has been developed to solve this problem. The adaptive optic SLO apparatus has an adaptive optic system that measures aberration of the eye being examined in real time using a wavefront sensor, and corrects aberration occurring in the eye being examined with regard to the measurement light and the returning light thereof using a wavefront correction device. This enables SLO images with high horizontal resolution (high-magnification image) to be acquired.
Such high-magnification images can be acquired as moving images, and are used for non-invasive observation of hemodynamic states. Retinal blood vessels are extracted from each frame, and the movement speed of blood cells through the capillaries, and so forth, are measured. Photoreceptors P are detected and the density distribution and array of the photoreceptors P measured, to evaluate the relationship with visual functions, using high-magnification images. FIG. 6B shows an example of a high-magnification image. The photoreceptors P, a low-luminance region Q corresponding to the position of capillaries, and a high-luminance region W corresponding to the position of a white blood cell, can be observed.
In a case of observing photoreceptors P or measuring distribution of photoreceptors P using a high-magnification image, the focus position is set nearby the outer layer of the retina (B5 in FIG. 6A) to take a high-magnification image such as in FIG. 6B. On the other hand, there are retinal blood vessels and capillaries that have branched running through the inner layers of the retinal (B2 through B4 in FIG. 6B). In cases of taking photographs of the eye to be examined, image region to be imaged may be larger than the angle of view high-magnification image. Cases of imaging widespread photoreceptor defect regions, cases of imaging a parafovea region which is an area of predilection for early-stage capillary lesions, and so forth, fall under such cases. Accordingly, Japanese Patent Laid-Open No. 2012-213513 discloses a technology to composite and display multiple high-magnification images acquired by shooting at different shooting positions.
Also, Japanese Patent Laid-Open No. 2013-169309 discloses a technology in which exceptional frames where effects of ocular microtremor in a high-magnification moving image of a certain shooting position are determined, and just the frames other than the exceptional frames determined in the high-magnification moving image are displayed.